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Diagenesis and burial history modeling of heterogeneous marginal marine to shoreface Paleocene glauconitic sandstones, Taranaki Basin, New Zealand

O'Neill, Sean R.; Jones, Stuart J.; Kamp, Peter J.J.

Diagenesis and burial history modeling of heterogeneous marginal marine to shoreface Paleocene glauconitic sandstones, Taranaki Basin, New Zealand Thumbnail


Authors

Sean R. O'Neill

Peter J.J. Kamp



Abstract

Paleocene marginal marine to shoreface glauconitic sandstones (F-Sands) of the Farewell Formation from the Maui Field in Taranaki Basin, New Zealand, demonstrate a diagenetic evolution driven by major shifts in acidic pore-water composition, rate of burial, and clay-mineral authigenesis. Mechanical compaction is the principal porosity-reducing mechanism during the first 2500 m of burial of the F-Sands. Continued mechanical compaction with long-grain contacts, concavo-convex contacts, and deformed liable grains are common throughout the F-Sands. Late-stage flow of dissolved CO2 in the pore fluids of the Farewell Formation is thought to have been generated from thermal decarboxylation of coaly source rocks. The circulation of these CO2-rich fluids will have dissolved into undersaturated pore fluids and partially catalyzed dissolution of feldspar and quartz, producing ions for the precipitation of kaolinite and chlorite. Timing of the diagenetic reactions, as determined using paragenetic observations, fluid-inclusion analysis, and burial history modeling, suggests that the quartz cements formed at a late stage (> 100°C, corresponding to 0–7 Ma) and is consistent with the migration of hydrocarbons, and associated CO2, into the F-Sand reservoir. Significant secondary porosity is generated through the dissolution of feldspar, which is preserved due to late-stage of occurrence at close to present-day maximum burial. Dissolved solutes in the F-Sands sandstones are being preferentially precipitated in interbedded and surrounding fine-grained heterolithic siltstone to very fine-grained sandstone beds, leading to enhanced heterogeneity and preservation of secondary porosity. This study provides an improved understanding for diagenetic reconstruction of marginal marine to shoreface facies.

Journal Article Type Article
Acceptance Date Dec 29, 2019
Online Publication Date Jun 30, 2020
Publication Date 2020-06
Deposit Date Jul 2, 2020
Publicly Available Date Jul 19, 2020
Journal Journal of Sedimentary Research
Print ISSN 1527-1404
Electronic ISSN 1938-3681
Publisher Society for Sedimentary Geology (SEPM)
Peer Reviewed Peer Reviewed
Volume 90
Issue 6
Pages 651-668
DOI https://doi.org/10.2110/jsr.2020.34
Public URL https://durham-repository.worktribe.com/output/1261492

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